1. Field of the Invention
The present invention relates to portable devices which, when activated, deliver ambient air in a compressed state, notwithstanding long periods of storage, for purposes of inflation and mechanical work, which devices are particularly useful in emergency situations for preventing loss of life and valuable equipment.
2. Brief Description of the Prior Art
Portable devices and systems are known in the prior art that are operable in emergency situations after long periods of storage for the inflation of aircraft escape slides, flotation bags, rafts and the like, and for mechanically cutting through vehicle bodies, fuselages and bulkheads. A common requirement of such devices is a capability for producing substantial amounts of power for relatively short periods of time. Portability of such devices, including the power source, is important inasmuch as it is impracticable in emergency situations to depend upon electrical outlets or internal combustion engine fuel as the source of the power.
Devices and systems currently in use for inflating structures such as aircraft escape slides, meet the foregoing requirements in respect of a "self-contained" power source by storing gases under high pressure in pressure vessels and utilizing them in emergency situations to actuate aspirators or turbofans. Inasmuch as the gases are stored over long periods of time, the pressure vessel must be hydrostatically pressure checked periodically, as required by the U.S. Department of Transportation, to determine if the pressure vessel contains enough gas to successfully operate an aspirator or turbofan.
It has been proposed in the prior art to provide the required self-contained power source in escape slide inflation installations in the form of a solid gas producing propellant, such as a rocket propellant. Such a power source is described in a paper by R. J. Richards published in SAFE ENGINEERING. August/September, 1970. A similar power source is described in U.S. Pat. No. 3,640,083, Galbraith et al.
The Richards paper describes a solid propellant "cool gas" generator for the direct inflation by the generated gas of aircraft emergency escape slides rafts, pontoons, and flotation bags. The inflation is through long lengths of tubing or hoses that are provided for the purpose of cooling the gas which, as generated is very hot, to a temperature that is compatible with the elastomers or fabrics used in the inflatable structure. The paper further describes such a generator used with a mixing chamber. aspirator, check valve. a nozzle and an auxiliary coolant such as a fluorinated and/or chlorinated hydrocarbon refrigerant for cooling the gases prior to delivering them through a hose connection to the inflatable structure. Depending upon aspirator efficiency the gases are stated to be delivered to the inflatable structure within 2 to 10 seconds, a volume output of 200 to 400 cu. ft. at pressures ranging from 1.5 to 3.0 psig. being developed. The weight of the generator is stated as ranging from 10 to 30 pounds including hoses and aspirators, the generator being 20 inches long with an outside diameter of 5 inches.
U.S. Pat. No. 3,640,083 discloses a solid propellant cool gas generator for inflating an aircraft escape slide in which a portion of the generated hot gases pressure feed as liquid from a storage chamber into a mixing zone for mixing with the liquid and causing vaporization, the liquid being a liquified fluorinated hydrocarbon type refrigerant, liquified carbon dioxide. liquified air, liquified ammonia, aqueous ammonia, water alone or a mixture of these listed materials. The vaporization of the liquid is stated to be attended by cooling of the hot gases. The relatively cool gases are conducted by a conduit to the structure to be inflated. Use of the gases for turbine operation also is mentioned.
There are problems in the application of such solid propellant cool gas generators for inflating inflatable structures. In terms of weight and volume of gas produced, the generators are inefficient whereby the volume of gas produced at a useful temperature and pressure is limited. Nitrogen/carbon dioxide mixtures that are used in inflation systems currently in use create significant operational problems because of the properties of carbon dioxide at low temperature, that is to say, its tendency to remain a liquid. This tendency results in a slow release of gas which results in unsatisfactory aspirator performance. Additionally, there is a tendency for the hoses to "kink" if not properly maintained thereby interfering with the proper operation of the system.
Devices utilizing gas producing propellants as a self-contained power source for mechanical cutting or other work-effecting purposes have been proposed in the prior art. Thus, U.S. Pat. No. 3,235,041, Schlidt et al discloses a portable power cutter wherein a turbine wheel is driven by the hot gases that are produced by a solid propellant gas generator. The turbine wheel is connected to effect driven rotation of a cutting tool shaft through a motion transmitting mechanism including a speed regulating assembly and speed reduction gears. The size of the cutter is described as being 34 inches long and 51/2 inches in diameter the weight without the cutting tool being 25 pounds. The cutter is said to be useful for cutting through metallic fuselages, body sections and bulkheads that present severe access problems in emergency situations.
U.S. Pat. No. 2,578,443, Nardone, discloses a fuel supply system that is mounted on a rocket motor and includes a solid propellant gas generator for driving a turbine wheel. The turbine wheel is connected through speed reduction gears to drive the shaft of a fuel pump which pumps liquid fuel from a tank to the combustion chamber of the rocket motor.
Because the turbine wheel turns many times faster than the driven shaft in the devices of each of the Schlidt et al and Nardone patents, the gear reduction is essential. This necessarily adds to the complexity, increases the weight, and reduces the efficiency of the device, and in the case particularly, of the Schlidt et al patent, detracts from its portability.
U.S. Pat. No. 3,417,566, Gould, discloses a portable tool for rotating a shaft to drive other tools and comprises a disposable fuel cartridge that produces heat through burning for generating steam in a boiler system. The steam is used to drive a piston swash plate type engine for rotating the shaft. Such a portable tool also is characterized by its complexity and inefficiency.